Kepler 20

So, more exciting news from the Kepler team: Kepler 20, a planetary system of five planets orbiting an Earth-like star 946 light years away in the constellation Lyra was announced at a NASA press conference yesterday. This time, none of the planets, from Kepler 20b through -f, were estimated to be orbiting within the habitable zone of Kepler 20 but instead had very short orbital periods of between 3 and 77 days, putting them all within the orbit of Mercury if superimposed onto our Solar System.  The importance of the Kepler 20 system is that two of the planets (-e and -f) are Earth-sized, or possibly even smaller, making them the smallest extrasolar planets yet discovered. The remaining three planets -b,-c and -d are sub-Neptune sized. I’ve done my best to illustrate their orbital configurations here (click for a better view):


Diagram of the Kepler 20 planetary system relative to the habitable zone distance, Earth and Jupiter. The mass estimates for Kepler 20e and -f is the mean of the upper and lower estimates provided by Fressin et al. (2011).


In terms of habitability, there is not much we can garner from the Kepler 20 planets. They are all in the ‘hot zone’ in very close proximity to the star. Their equilibrium temperatures are likely to range from 1014 °K (Kepler 20b) to 369 °K (Kepler 20d) – much too hot to host terrestrial biology within our current experience and understanding. It is possible, within ‘theoretical considerations‘ (i.e. planet formation model output), that Kepler 20e and -f are rocky, and that Kepler 20d may have a thick water-vapour atmosphere.

The larger Kepler 20 b, -c and -d were detected using a combination of photometry and astrometry, but due to their relatively small photometric and/or gravitational effect, the smaller Kepler 20 planets were uncovered using a statistical method that excluded the possibility that the detected signal was caused by a binary star eclipsing Kepler 20. The Kepler team have now provided proof that they are able to detect Earth-sized planets, even in very short period orbits. Coupled with the discovery of Kepler 22b in the habitable zone a few weeks ago, their brief of discovering Earth-like planets with the habitable zone of distant stars is partially complete – all we need now is to find an Earth-sized planet, like Kepler 20e, in the habitable zone, like Kepler 22b. It really is only a matter of time now.

Uninhabitable planets in the Habitable Zone.

Following the excitement surrounding the discovery of potentially Earth-like exoplanet Kepler 22-b (K22-b) earlier this week, the ‘habitable zone’ (HZ) concept is becoming increasingly important to our interpretation of these announcements. Used unilaterally, the HZ metric may be misleading and it should be considered as a rough guide, interpreted relative to other available planetary characteristics.

The HZ describes the theoretical distance (with both upper and lower limits) at which a given planet must orbit a star to support the basic fundamental requirements for the emergence of life based on our understanding of the evolution of the biosphere on Earth. The HZ theory is based on terrestrial (rocky, as opposed to gaseous or icy) planets that exhibit dynamic tectonic activity, that have active magnetospheres and atmospheres of water, carbon dioxide and nitrogen with liquid water available at the surface. Liquid water is the key; the giver of life and the fundamental factor in defining the HZ in any planetary system.

It should be relatively easy to spot a number of limitations of the HZ concept already; we are still unsure of the composition of K22-b which would significantly affect any habitability analysis.  Also, we assume that exobiology would have the same requisites for life which may not necessarily be so; this alludes to our inability to detach ourselves from our anthropic bias. The ubiquity of extremophilic organisms (those able to tolerate extremes of temperature, pressure, salinity, radiation etc.) on Earth has also lent some credence to the extension of the parameters of the habitable zone beyond those originally included. All in all, the idea of a habitable zone is a great thought experiment, but it may not necessarily translate into reality. Planetary processes, such as tectonics and atmospheric greenhouse effects, warp the boundaries of the HZ. Astronomers are now considering the very real possibility of liquid water existing in sub-surface oceans of Jupiter’s moon Europa, a body well outside of the habitable zone of our solar system.

I think that the hype surrounding the discovery of K22-b has highlighted the limitations of using the habitable zone concept in isolation when considering the potential for life on other planets. It certainly provides an excellent starting point to narrow down the enormous Kepler catalogue, and it will play an important role in identifying habitable planet candidates in the future. Clearly however, other factors need to be taken into consideration. I’ve seen numerous articles and posts describing Kepler 22-b as “Earth’s twin” and “Earth 2.0″ based solely on the fact that it has been discovered to be orbiting within the habitable zone of Kepler 22. What is usually skipped over, or not mentioned at all, is that K22-b has a radius 2.4 times that of the Earth, and estimates of its mass range from 10 to 34 times that of our planet. With a surface gravity possibly nearing 6 g, an ‘Earth-twin’ this is not. My favourite resource for planetary habitability, the Habitable Exoplanet Catalog run by UPR Arecibo has released an updated best and worst case scenario analysis for K22-b:

I covered the worst case scenario in my last post, but here it is again (updated):

Kepler-22 b habitability assessment from the HEC

A gaseous planet with huge mass and crushing gravity, and still a very hot 42 °C for those that can stand being squished to a pulp. With a greenhouse atmosphere similar in composition to that of the Earth, the temperature would be roughly -15 °C; with Venus’ super-greenhouse, the surface would be closer to a lead-melting 460 °C.

This estimation is based on an ocean planet with a rocky core, no continents and thick cloud cover.  It’s mass has been downgraded slightly, but its still an impressive ~10 times that of Earth. Its surface gravity isn’t quite as oppressive as first thought, but it would still be very uncomfortable especially in the heat. The conclusion is that it would be habitable, but only at a push, and you certainly wouldn’t choose to spend your summer holidays on Kepler 22-b.

I can only reiterate the conclusions of my last post; it’s important not to over-hype planets that are only borderline habitable in the very best case scenario. It’s unscientific and will be damaging to the public perception of exoplantology in the long run. There are only so many times that the exoplanet community can cry wolf and expect the public to be interested in these kind of Earth analogue stories. When an excellent candidate comes along, which I firmly believe that it will, there is a risk that this monumental announcement will be made to an empty room.

Kepler 22-b

The recent announcement of the discovery of planet Kepler 22-b has been met with great excitement. Google search returns over 12 million results for the term ‘Kepler 22-b’ and the discovery has been extensively covered by the mainstream media, an usual situation and one that has not been afforded to many other exoplanet announcements. It’s clear that the possibility that this distant world may be suitable for life (as we understand it) has spurred the imagination of scientists and the public alike. Kepler 22-b has been calculated to be orbiting well within the habitable zone (a term used often in astrobiology, and one that I have discussed in some depth here) of its Sun-like G5 star Kepler 22, but this is not the only factor controlling the habitability of a planet.

Yesterday I covered the launch of the new Habitable Exoplanet Catalogue (HEC), which provided an excellent resource and standardisation tool for assessing the possible habitability of newly discovered planets. In the last few hours, the HEC team has released a provisional assessment of Kepler-22b, based on their habitability metrics, and their findings are summarised by the graphic below:

Habitability analysis of Kepler 22-b by the team at the Habitable Exoplanet Catalogue

So whilst Kepler-22b is comfortably within the habitable zone, it’s huge mass and crushing gravity effectively rules out the possibility of terrestrial life. The planetary temperature given here (313 °K or 40 °C)  seems more realistic than that reported in the press (295 °K or 22 °C)  but I am yet to find the official figure. Accordingly, it is classified as a non-habitable warm neptunian exoplanet.

Below is a table listing some of the characteristics of Kepler 22-b. At the top of the table is the information that has been garnered on the planet and star from photometry to a reasonable degree of accuracy. At the bottom however, are comparisons of Kepler 22-b based on the two likely composition and mass outcomes, which can only be confirmed with more information. I use the terms ‘best’ case and ‘worst’ case relative to terrestrial habitability. I’ve discussed these figures in more detail here.

Kepler 22-b characteristics table. ‘Best’ and ‘worst’ case scenarios are in reference to terrestrial habitability

It’s wonderful to see that exoplanet science is featuring so prominently in the media and is being discussed outside the dusty confines of academia. The Kepler team deserves high praise and recognition for their exciting and relevant work. However, with hundreds more Kepler candidate planets due to be announced, we should be careful not to hype planets like Kepler-22b too much. It would be a travesty if the public (our funding source, remember) loses interest after repeated ‘nearly Earth’ stories (akin to Gliese 581 g) and misses the significance of a truly wonderful, unique and decisively habitable Earth-like planet discovered in the near future.

#EDIT (17/12): Inserted characteristics table into post.

The Habitable Exoplanets Catalog

The Habitable Exoplanet Catalog (HEC), a project by University of Puerto Rico (UPR) at Arecibo, went online on the 5th of December and after a brief peruse I felt compelled to express my approval and appreciation in blog form as soon as possible! A brief description, taken from the UPR Acecibo site:

The HEC is the first extensive catalog on the number, diversity, and characteristics of habitable exoplanets in the universe. It uses new developments by the PHL [Planetary Habitability Laboratory] like the Earth Similarity Index (ESI), the Habitable Zones Distance (HZD), classification systems, and comparisons with Earth past and present, to help assess the habitability of exoplanets.

The project uses three habitability metrics as well as two classification systems to assess the relative similarity and potential habitability of a number of exoplanets that have been announced and proposed but awaiting confirmation. These indices are built from observational data, but also from model output. The results, which at the moment outline 16 possibly habitable exoplanets, are presented via awesome individual graphics, thus:

KOI 736.01

This is exoplanet KOI 736.01 (as always, a wonderfully enigmatic name), a Kepler candidate considered to be ‘most similar’ to Earth based on the new habitability rating system. Awesome, right? Along with general planetary characteristics (part observational, part modelled) there are also some interesting classifications (mesoplanet, terran etc.) and some unusual indices (ESI, SPH, HZD) on the right. Let’s explore these in some detail, using KOI 736.01 as our case study. The classification methodology is described by the authors here.

Firstly, the classifications. The Planetary Class (pClass) sorts planets according to three thermal divisions (hot, warm, cold) and seven mass divisions, which are, in ascending order: asteroidan, mercurian, subterran, terran, superterran, neptunian, and jovian. KOI 736.01 is a warm terran planet, meaning that it is within the habitable zone of its star and of a comparable mass to Earth. Class M (mesoplanet) alludes to the fact that KOI 736.01 has a surface temperature of between 0 – 50 °C according to the Habitable Class classification (hClass). Other divisions in hClass range from extremely cold hypopsychroplanets through to very hot hyperthermoplanets.

Great so far, now lets turn our attention to the habitability metrics on the right. ESI or the Earth Similarity Index uses several planetary characteristics, namely radius, density, escape velocity, and surface temperature to determine the relative similarity of the planet to Earth on a scale from 0 (completely dissimilar) to 1 (identical). Our chosen planet has an ESI of 0.98, making it very like Earth and therefore likely to harbour a rocky interior and terrestrial atmosphere. This shouldn’t come as too much of a surprise; based on the general characteristics (mass, radius, gravity and period) included in the graphic it is fairly easy to ascertain that this is a planet very similar to our own, with the exception of a very brief orbital period. SPH, or the Standard Primary Habitability is a measure, calculated from surface temperature and humidity, of the ability of the planet to support terrestrial primary producers and in turn estimate the net primary productivity that would be expected. 0 is very unproductive and 1 is more so. With a SPH of 0.63, KOI 736.01 is moderately productive and very similar to the Earth at 0.65. SPH makes the assumption that water would be present, given a surface temperature of between 0 and 100 °C but in my opinion this may not always be the case. The final metric, HZD stands for Habitable Zone Distance, and describes the position of the planet within the habitable zone: +1 is on the very outer edge, 0 in the middle and planets with a HZD of -1 are straddling the inner edge. Accordingly, with a HZD of -0.59, KOI 736.01 is about half-way between the very centre of habitable zone and its inner edge.

All in all, the Habitable Planet Catalog is a wonderful resource with the potential to increase the accessibility of exoplanet science substantially. It also provides an excellent standardisation methodology that I hope will be readily adopted by other scientists for coherence and comparison. Bearing in mind my analysis was only based on one small area of the site dedicated to Earth-similarity, I suggest that anyone interested in the habitability of extra-solar planets takes the time to wonder around this great site and explore it in more detail.


Follow Professor Abel Mendez, the principal investigator at the PHL, on Twitter here.

Stanislaw Burzynski: Cancer, Lawsuits and Intimidation

I’ve been watching the unravelling scandal surrounding the ‘pioneering’ cancer treatment of a certain Dr Stanislaw Burzynski with interest for some time now. Since music journalist Luke Bainbridge published this article in the Observer 3 weeks ago, things have moved rather quickly. This is a heart-wrenching account of a family blighted by cancer; his sister-in-law was undergoing chemotherapy for breast cancer when it was discovered that her daughter, 4 year-old Billie, had an inoperable brain tumour. The 2-year survival rate for this form of cancer is ~10%, and in the UK radiotherapy offered by the NHS would, at best, reduce symptoms temporarily. By all accounts, an awful and unimaginably distressing situation for any family to find themselves in. However, the catalyst for the building scandal become evident when Luke outlined the lengths that well-meaning celebrities and concerned citizens have gone to to help raise money to send young Billie for treatment at Burzynski’s Texas-based clinic. The estimated cost of treatment is £200,000. A similar campaign called Hope for Laura also emerged, this time in an attempt to raise £150,000 to finance the treatment of a young mother with brain cancer.

The clinic utilises a treatment called ‘Antineoplaston’ therapy (a brilliant pseudoscientific moniker, to be honest) which involves administering several peptides, amino acids and their derivatives, originally synthesised from blood and urine but now produced from commercially available chemicals, under the hypothesis that these compounds operate as ‘molecular switches’ that may be useful in combating cancers. This is not a new idea and was originally theorised by Burzynski in 1976. Since then, the vast majority of research has been carried out by him or his team to limited or no measurable success. To quote the US National Cancer Institute:

“No randomized controlled trials showing the effectiveness of antineoplastons have been published in the peer-reviewed scientific literature.”

The treatment is not approved by the US FDA (Food and Drug Administration) and therefore cannot be administered as a prevention or cure. Because of this ruling, the Burzynski Clinic is charging hundreds of thousands for desperate patients to be admitted on to ‘clinical trails’, a peculiar loophole in US law, that seem to have no end in sight.

Here in the UK, Cancer Research published this balanced post on their blog, stating:

“At the moment, Burzynski’s antineoplaston treatment has to be regarded as experimental and unproven.”

 At this point I feel I should point out, if it wasn’t already obvious from the subject areas of rest of my posts, that I am not a trained biochemist, oncologist or pharmacist, and make no claim to be an expert in any field that Dr Burzynski operates. Yes, I was shocked that an article had made it though the Observer’s editorial process without the above concerns being raised, but at that time I felt that wading into debate in an unfamiliar area would be a bad idea. Besides, the blogosphere is a big place and there are many excellent bloggers out there who are well versed in the field of ‘quackbusting’ and who have my full support. One such blogger is Andy Lewis of the Quackometer, who wrote this concise post in response to the original Observer article.

However, in the wake of this article a tirade of vitriolic frothy-mouthed emails were sent to Andy and also to 17-year-old quackbuster extraordinaire Rhys Morgan by Burzynski Clinic ‘representative’ Marc Stephens, who threatened libel, lawsuits and used a level of heavy-handedness that was certainly tantamount to intimidation, if not assault. Mr Stephens had all the pretensions of an attorney, but with none of the professionalism, candour or qualifications to support them. It soon became apparent that he was a employed in a ‘P.R. marketing and sponsorship’ role. If Burzynski was aware of what Stephens was doing in his name, this was not the work of a scientist, doctor or decent human being.  The rallying cry was sounded and the Streisand effect lurched into action . Since then over 100 articles have been written exposing every aspect of the Burzynski empire, from their threats and intimidatory tactics, to their rubbish science and non-existent peer-reviewed publications. This post by the Anarchic Teapot on some those who Burzynski has failed is particularly upsetting.

For me, the final straw came in the form of today’s Observer editorial. Considering the underhanded tactics that (the now unemployed) Marc Stephens had adopted in an attempt to silence Burzynski’s critics, and despite the lack of evidence for the efficacy of his treatments, the crux of the article smeared the UK bloggers as the trolls and claimed the response was insensitive to the families of those behind the campaigns. It was semi-apologetic to Burzynski, spineless and frankly appalling. In every conceivable situation, it is better to know the truth than seek comfort in a lie, and it is for this reason that I am writing this post. No, I’m not a doctor but I am a reasonable, rational human being and I can no longer stand back and watch whilst this man extracts the life-savings of desperate people by misappropriating science for his own corrupt means.

No one who has written critically about Burzynski has done so in spite of the campaigns mentioned above. It doesn’t take a medical doctor or scientist to discover that antineoplaston therapy does not work, and one of the most distressing parts of this entire affair is the cost. Hundreds of thousands of pounds (or dollars) are raised to finance the futile work of a charlatan, when there are many more legitimate cancer charities and research institutes much more deserving of such contributions. This is a travesty. It is unashamed, blatant and transparent extortion of the most abhorrent variety. Like vultures, snake oil salesmen prey on the desperate, the frightened. Empty promises abound and hope is delivered prematurely and without sincerity. With all avenues exhausted and the battle nearly lost, the vultures swoop.

Perhaps Burzynski’s worst crime of all is the fact that he robs people of time. Time is a valuable commodity, especially for those with inoperable tumours, and when nearing empty this precious resource should be spent sparingly amongst family and friends. Instead of coming to terms with the inevitable, however unjust and distressing, desperate parents, husbands and wives invest this most invaluable of currencies as hope in the unfounded claims of people like Stanislaw Burzynski.